I just opened a 100g bag of tea from Maiko and the package is resealable. I would have usually poured the 100g into a tea tin and would open/close that tin often as I worked through the tea. Light bulb went on and I thought it's probably better to only pour in 50g, and leave the other 50g in the original bag, with the air pressed out, and resealed. I have to assume this is preferrable but will ask - am I'm missing something with this approach?

Also, when the 100g bag isn't resealable, I was just thinking that it would make sense to pour 50g into one tin for immemdiate use, and the other 50g into a 2nd tin that I wouldn't open again until I'm done the first tin. Again, have to assume this is a fine approach but I will ask if I'm missing something?

Sounds about right! I always separate my 100 gram teabags into 25 or 50 grammers. I try to place these smaller amaounts in as small containers or resealable bags as possible.

Prior to doing it this way, my opened sencha would be quite noticeably "off" in as little as 30 days. Now I can keep opened sencha for extended periods with little to know degrading, especially when accompanied by cold storage of the unused portion.

My storage variation for Japanese greens is based on earlier postings by Chip. I have small tight lidded sample tins that each hold about 35 grams or so of Japanese greens. 3 of these fit in one of my beautiful washi covered doubled lidded tea tins. When I open a new 100 gram bag I divide the tea among 3 sample tins and then put all 3 in one washi tin. That way only one tin of tea at a time is exposed to light and air and no gyo or Sencha is ever lost in the tea cabinet. My sample tins came from Upton teas but I'm sure there are other sources. If not, Upton is a good source for rooibos and herbals.

I do the same, with Upton's sample tins, also based on Chip's posts Having your tea pre-sorted into small portions also makes for easy transport in case you want to grab a couple to take to the office or a friend's house.